The invention relates to fuel systems with pressure regulation.
In a returnless fuel supply system for a fuel injected engine, a certain fuel pressure must be maintained at the fuel rail during engine operation and after the engine is turned off. This pressure regulation can be done mechanically or electronically when the engine is on and mechanically when the engine is off. When the pressure regulation is electronic, the pump voltage is varied to maintain the set pressure. It is desirable to provide pressure relief for hot soak conditions, which frequently occur, for example, when the engine is turned off after operating long enough to open the coolant thermostat.